1. Field of the Invention
The present invention relates to a semiconductor memory device such as a programmable read-only memory (PROM) incorporating a logic generating circuit for an identification code including a manufacturer's code and a device code.
2. Description of the Related Art
Generally, semiconductor memory devices such as PROM's incorporate logic circuits for generating identification codes indicating the function thereof. For example, in a PROM, an identification code is ulilized to specify a programming process applied thereto. In this case, the identification code is output before a programming mode to indicate a programming voltage such as 21 V, 12 V, or the like for the PROM. Then, a writing operation is actually performed by a programming device upon the PROM by using the identified voltage.
In a prior art PROM, a logic circuit for generating an identification code is interposed within a data path for passing an internal read data signal to an output terminal. As a result, such a logic circuit is a hindrance to high-speed transmission of an internal read data signal, thus reducing the speed of the read operation. This will be explained later.